The combustion and explosion characteristics of lithium-ion battery vent gas is a key factor in determining the fire hazard of lithium-ion batteries.Investigating the combustion and explosion hazards of lithium-ion ba...The combustion and explosion characteristics of lithium-ion battery vent gas is a key factor in determining the fire hazard of lithium-ion batteries.Investigating the combustion and explosion hazards of lithium-ion batteries vent gas can provide guidance for rescue and protection in explosion accidents in energy storage stations and new energy vehicles,thereby promoting the application and development of lithium-ion batteries.Based on this understanding and combined with previous research on gas production from lithium-ion batteries,this article conducted a study on the combustion and explosion risks of vent gas from thermal runaway of 18650 LFP batteries with different states of charge(SOCs).The explosion limit of mixed gases affected by carbon dioxide inert gas is calculated through the“elimination”method,and the Chemkin-Pro software is used to numerically simulate the laminar flame speed and adiabatic flame temperature of the battery vent gas.And the concentration of free radicals and sensitivity coefficients of major elementary reactions in the system are analyzed to comprehensively evaluate the combustion explosion hazard of battery vent gas.The study found that the 100%SOC battery has the lowest explosion limit of the vent gas.The inhibitory elementary reaction sensitivity coefficient in the reaction system is lower and the concentration of free radicals is higher.Therefore,it has the maximum laminar flame speed and adiabatic flame temperature.The combustion and explosion hazard of battery vent gas increases with the increase of SOC,and the risk of explosion is the greatest and most harmful when SOC reaches 100%.However,the related hazards decrease to varying degrees with overcharging of the battery.This article provides a feasible method for analyzing the combustion mechanism of vent gas from lithium-ion batteries,revealing the impact of SOC on the hazardousness of battery vent gas.It provides references for the safety of storage and transportation of lithium-ion batteries,safety protection of energy storage stations,and the selection of related fire extinguishing agents.展开更多
The high temperature heat pump and desiccant wheel(HTHP&DW) system can make full use of heat released from the condenser of heat pump for DW regeneration without additional heat. In this study, DW operation in the...The high temperature heat pump and desiccant wheel(HTHP&DW) system can make full use of heat released from the condenser of heat pump for DW regeneration without additional heat. In this study, DW operation in the HTHP&DW system was investigated experimentally, and the optimization analysis of HTHP&DW system was carried out. The performance of DW had influence on the dehumidification(evaluated by dehumidification and regeneration effectiveness) and cooling load(evaluated by thermal and adiabatic effectiveness). The results show that the enthalpy increase occurred in all the experiments. Compared to the isosteric heat, heat accumulation in the desiccant and matrix material and heat leakage from regeneration side to process side have greater influence on the adiabatic effectiveness. Higher regeneration temperature leads to lower adiabatic effectiveness that increases more cooling load of the system. When the regeneration temperature is 63℃, the maximal dehumidification effectiveness is 35.4% and the satisfied adiabatic effectiveness is 88%, which contributes to the optimal balance between dehumidification and cooling.展开更多
The heat How generated from the infinite rock mass surrounding the underground tunnels is a major cause for the increasing cooling demands in deep mine tunnels.Insulation layers with lower thermal conductivities on tu...The heat How generated from the infinite rock mass surrounding the underground tunnels is a major cause for the increasing cooling demands in deep mine tunnels.Insulation layers with lower thermal conductivities on tunnel walls and roof ceilings are believed to supply a thermo-barrier for heat abatement.However,it is found that no systematic theoretical investigations were made to predict and confirm the effectiveness of underground thermal insulation.Specifically,investigations on the underground insulation problems involving heat flows through the semi-infinite hot rock mass and insulation layer were not sufficient.Thus,in this paper,the thermal characteristics,accompanied with heat flow through the semi-infinite rock mass and the insulation layer,were modeled by both analytical and numerical methods with focus on underground mine tunnels.The close agreements between models have indicated that the thermal insulation applied on tunnel surfaces is able to provide promising heat abatement effects.展开更多
With a thermal manikin, the distribution pattern of thermal insulation in multi-layered clothing ensemble is studied. It is found that the thermal insulation of multi-layered clothing ensemble has certain statistical ...With a thermal manikin, the distribution pattern of thermal insulation in multi-layered clothing ensemble is studied. It is found that the thermal insulation of multi-layered clothing ensemble has certain statistical relationship with the thermal insulation of each layer, and the prediction equation has been established.展开更多
According to 350 MW and 600 MW boilers,under oxygen fuel condition,through the reasonable control of the primary and secondary flow and the correct option and revision of mathematical model,the temperature distributio...According to 350 MW and 600 MW boilers,under oxygen fuel condition,through the reasonable control of the primary and secondary flow and the correct option and revision of mathematical model,the temperature distribution,heat flux distribution and absorption heat distribution,etc.was obtained which compared with those under air condition.Through calculation,it is obtained that the primary and secondary flow mixed well,good tangentially fired combustion in furnace was formed,the temperature under air condition obviously higher than the temperature under O26 condition.The adiabatic flame temperature of wet cycle was slightly higher than that of dry cycle.The maximum heat load appeared on the waterwall around the burner area.The heat load gradually decreased along the furnace height up and down in burner area.The heat absorption capacity of the furnace under O26 was lower than that under the air condition.The heat absorption capacity of the platen heating surface under 026 was equal to that under air condition.And the heat absorbing capacity of waterwall under O26 was about 7%~12% less than that under air condition.展开更多
Analogizing with the heat conduction process, the entransy dissipation extremum principle for thermal insulation process can be described as: for a fixed boundary heat flux (heat loss) with certain constraints, the th...Analogizing with the heat conduction process, the entransy dissipation extremum principle for thermal insulation process can be described as: for a fixed boundary heat flux (heat loss) with certain constraints, the thermal insulation process is optimized when the entransy dissipation is maximized (maximum average temperature difference), while for a fixed boundary temperature, the thermal insulation process is optimized when the entransy dissipation is minimized (minimum average heat loss rate). Based on the constructal theory, the constructal optimizations of a single plane and cylindrical insulation layers as well as multi-layer insulation layers of the steel rolling reheating furnace walls are carried out for the fixed boundary temperatures and by taking the minimization of entransy dissipation rate as optimization objective. The optimal constructs of these three kinds of insulation structures with distributed thicknesses are obtained. The results show that compared with the insulation layers with uniform thicknesses and the optimal constructs of the insulation layers obtained by minimum heat loss rate, the optimal constructs of the insulation layers obtained by minimum entransy dissipation rate are obviously different from those of the former two insulation layers; the optimal constructs of the insulation layers obtained by minimum entransy dissipation rate can effectively reduce the average heat loss rates of the insulation layers, and can help to improve their global thermal insulation performances. The entransy dissipation extremum principle is applied to the constructal optimizations of insulation systems, which will help to extend the application range of the entransy dissipation extremum principle.展开更多
The I-V characteristic of a superconductor is generally described by power-law,in which the superconductor with a high n transfers quickly from superconducting state to the normal conducting state.With a high transpor...The I-V characteristic of a superconductor is generally described by power-law,in which the superconductor with a high n transfers quickly from superconducting state to the normal conducting state.With a high transport current,in the low n value area,flux flow voltage becomes lower than in the high n value area,so that the transient characteristics strongly affect its stability.Based on those properties,we propose a new hybrid conductor which is made of low temperature superconductor(LTS) and high temperature superconductor(HTS) with concentric configuration in which the HTS coat is located outside of the LTS core.According to their power-law models,the modified adiabatic and dynamic stability criteria are qualitatively obtained by taking account into not only their critical currents but also n values.As a result,the new hybrid conductors have potential applications with higher engineering current density and improved stability.展开更多
基金supported by the National Natural Science Foundation of China(52106284)the Natural Science Foundation of Hebei Province(B2021507001)support of Project to Promote Innovation in Doctoral Research at CPPU(BSKY202302).
文摘The combustion and explosion characteristics of lithium-ion battery vent gas is a key factor in determining the fire hazard of lithium-ion batteries.Investigating the combustion and explosion hazards of lithium-ion batteries vent gas can provide guidance for rescue and protection in explosion accidents in energy storage stations and new energy vehicles,thereby promoting the application and development of lithium-ion batteries.Based on this understanding and combined with previous research on gas production from lithium-ion batteries,this article conducted a study on the combustion and explosion risks of vent gas from thermal runaway of 18650 LFP batteries with different states of charge(SOCs).The explosion limit of mixed gases affected by carbon dioxide inert gas is calculated through the“elimination”method,and the Chemkin-Pro software is used to numerically simulate the laminar flame speed and adiabatic flame temperature of the battery vent gas.And the concentration of free radicals and sensitivity coefficients of major elementary reactions in the system are analyzed to comprehensively evaluate the combustion explosion hazard of battery vent gas.The study found that the 100%SOC battery has the lowest explosion limit of the vent gas.The inhibitory elementary reaction sensitivity coefficient in the reaction system is lower and the concentration of free radicals is higher.Therefore,it has the maximum laminar flame speed and adiabatic flame temperature.The combustion and explosion hazard of battery vent gas increases with the increase of SOC,and the risk of explosion is the greatest and most harmful when SOC reaches 100%.However,the related hazards decrease to varying degrees with overcharging of the battery.This article provides a feasible method for analyzing the combustion mechanism of vent gas from lithium-ion batteries,revealing the impact of SOC on the hazardousness of battery vent gas.It provides references for the safety of storage and transportation of lithium-ion batteries,safety protection of energy storage stations,and the selection of related fire extinguishing agents.
基金Supported by the Danish International DSF Project(No.09-71598)Chinese International Collaboration Project(No.2010DFA62410)
文摘The high temperature heat pump and desiccant wheel(HTHP&DW) system can make full use of heat released from the condenser of heat pump for DW regeneration without additional heat. In this study, DW operation in the HTHP&DW system was investigated experimentally, and the optimization analysis of HTHP&DW system was carried out. The performance of DW had influence on the dehumidification(evaluated by dehumidification and regeneration effectiveness) and cooling load(evaluated by thermal and adiabatic effectiveness). The results show that the enthalpy increase occurred in all the experiments. Compared to the isosteric heat, heat accumulation in the desiccant and matrix material and heat leakage from regeneration side to process side have greater influence on the adiabatic effectiveness. Higher regeneration temperature leads to lower adiabatic effectiveness that increases more cooling load of the system. When the regeneration temperature is 63℃, the maximal dehumidification effectiveness is 35.4% and the satisfied adiabatic effectiveness is 88%, which contributes to the optimal balance between dehumidification and cooling.
基金The financial support from an Engage Grant in the Natural Sciences and Engineering Research Council(NSERC),Canada,is gratefully acknowledged
文摘The heat How generated from the infinite rock mass surrounding the underground tunnels is a major cause for the increasing cooling demands in deep mine tunnels.Insulation layers with lower thermal conductivities on tunnel walls and roof ceilings are believed to supply a thermo-barrier for heat abatement.However,it is found that no systematic theoretical investigations were made to predict and confirm the effectiveness of underground thermal insulation.Specifically,investigations on the underground insulation problems involving heat flows through the semi-infinite hot rock mass and insulation layer were not sufficient.Thus,in this paper,the thermal characteristics,accompanied with heat flow through the semi-infinite rock mass and the insulation layer,were modeled by both analytical and numerical methods with focus on underground mine tunnels.The close agreements between models have indicated that the thermal insulation applied on tunnel surfaces is able to provide promising heat abatement effects.
文摘With a thermal manikin, the distribution pattern of thermal insulation in multi-layered clothing ensemble is studied. It is found that the thermal insulation of multi-layered clothing ensemble has certain statistical relationship with the thermal insulation of each layer, and the prediction equation has been established.
文摘According to 350 MW and 600 MW boilers,under oxygen fuel condition,through the reasonable control of the primary and secondary flow and the correct option and revision of mathematical model,the temperature distribution,heat flux distribution and absorption heat distribution,etc.was obtained which compared with those under air condition.Through calculation,it is obtained that the primary and secondary flow mixed well,good tangentially fired combustion in furnace was formed,the temperature under air condition obviously higher than the temperature under O26 condition.The adiabatic flame temperature of wet cycle was slightly higher than that of dry cycle.The maximum heat load appeared on the waterwall around the burner area.The heat load gradually decreased along the furnace height up and down in burner area.The heat absorption capacity of the furnace under O26 was lower than that under the air condition.The heat absorption capacity of the platen heating surface under 026 was equal to that under air condition.And the heat absorbing capacity of waterwall under O26 was about 7%~12% less than that under air condition.
基金supported by the National Key Basic Research and Development Program of China (‘973’ Program) (Grant No. 2012CB720405)the National Natural Science Foundation of China (Grant No. 51176203)the Natural Science Foundation for Youngsters of Naval University of Engineering (Grant No. HGDQNJJ11008)
文摘Analogizing with the heat conduction process, the entransy dissipation extremum principle for thermal insulation process can be described as: for a fixed boundary heat flux (heat loss) with certain constraints, the thermal insulation process is optimized when the entransy dissipation is maximized (maximum average temperature difference), while for a fixed boundary temperature, the thermal insulation process is optimized when the entransy dissipation is minimized (minimum average heat loss rate). Based on the constructal theory, the constructal optimizations of a single plane and cylindrical insulation layers as well as multi-layer insulation layers of the steel rolling reheating furnace walls are carried out for the fixed boundary temperatures and by taking the minimization of entransy dissipation rate as optimization objective. The optimal constructs of these three kinds of insulation structures with distributed thicknesses are obtained. The results show that compared with the insulation layers with uniform thicknesses and the optimal constructs of the insulation layers obtained by minimum heat loss rate, the optimal constructs of the insulation layers obtained by minimum entransy dissipation rate are obviously different from those of the former two insulation layers; the optimal constructs of the insulation layers obtained by minimum entransy dissipation rate can effectively reduce the average heat loss rates of the insulation layers, and can help to improve their global thermal insulation performances. The entransy dissipation extremum principle is applied to the constructal optimizations of insulation systems, which will help to extend the application range of the entransy dissipation extremum principle.
基金supported in part by the National Natural Science Foundation of China (Grant No. 51077051)
文摘The I-V characteristic of a superconductor is generally described by power-law,in which the superconductor with a high n transfers quickly from superconducting state to the normal conducting state.With a high transport current,in the low n value area,flux flow voltage becomes lower than in the high n value area,so that the transient characteristics strongly affect its stability.Based on those properties,we propose a new hybrid conductor which is made of low temperature superconductor(LTS) and high temperature superconductor(HTS) with concentric configuration in which the HTS coat is located outside of the LTS core.According to their power-law models,the modified adiabatic and dynamic stability criteria are qualitatively obtained by taking account into not only their critical currents but also n values.As a result,the new hybrid conductors have potential applications with higher engineering current density and improved stability.
